UPSC Combined Geo-Scientist, Mains · 2018 · Mains Paper II
Q1(o). Second Balmer line
Question
Which transition gives the second Balmer line: (i) 4p→3s; (ii) 2s→4p; (iii) 3d→2p; (iv) 4d→2p; (v) 4d→3p? Give reasons.
Answer in brief
Option (iv), 4d→2p, is the second Balmer emission line (Hβ).
Key points
- Balmer emission lines terminate at n=2. The first is n=3→2; the second is n=4→2.
- 4d→2p has the correct principal levels and satisfies the electric-dipole rule Δl=-1.
- 3d→2p is the first Balmer line. Transitions ending at n=3 belong to the Paschen series.
The full model answer
As written for the answer booklet: the diagram carries the working, the lines stay short. Read here only; it is not offered as a download.
CoversSecond Balmer lineAtomic spectroscopy
All parts of Question 1
- 1(a) Equal molecular speeds5 marks
- 1(b) Fugacity under repulsion5 marks
- 1(c) Wetting of glass5 marks
- 1(d) FCC particle count5 marks
- 1(e) Joule–Thomson cooling5 marks
- 1(f) Gibbs and Helmholtz changes5 marks
- 1(g) Equilibrium-constant conventions5 marks
- 1(h) Very dilute hydrochloric acid5 marks
- 1(i) Pressure controlling boiling5 marks
- 1(j) Primary kinetic salt effect5 marks
- 1(k) Heat of spontaneous adsorption5 marks
- 1(l) Conductivity as an intensive property5 marks
- 1(m) Anthracene photodimerization5 marks
- 1(n) Particle-in-a-box eigenvalue5 marks
- 1(o) Second Balmer line5 marks
- 1(p) Normal-mode counts5 marks